Efficient parallel resolution of pentafluorophenyl active esters using quasi-enantiomeric combinations of oxazolidin-2-ones

The parallel resolution of racemic pentafluorophenyl 2-aryl/phenylpropanoates and butanoates using an equimolar combination of quasi-enantiomeric Evans oxazolidin-2-ones is discussed. The levels of diastereoselectivity were excellent (>90% de) leading to separable quasi-enantiomeric oxazolidin-2-ones in good yield. This methodology was used to resolve a series of structurally related 2-aryl/phenylpropanoic and butanoic acids.     

Resolution of pentafluorophenyl esters using oxazolidin-2-ones

A series of structurally related racemic pentafluorophenyl active esters were resolved using an equimolar amount of (S)-4-phenyloxazolidin-2-one. The levels of diastereocontrol were found to be excellent (80-96% de) at ∼40% conversion.     

Synthesis of oxazolidin-2-ones using carbonate ion on a polymeric support

Through the insertion of a carbon dioxide molecule, the oxazolidin-2-ones ($\text{5a}$) and ($\text{5b}$) were prepared by treataent of the salts ($\text{4a}$) and ($\text{4b}$) with carbonate anion on polymeric support. The hydrolysis under basic conditions of ($\text{5a}$) and ($\text{5b}$) afforded the erythro-3-amino-1,2-diols ($\text{6a}$) and ($\text{6b}$) which were fully acetylated: the 2-amino-2-deoxyerythritol derivative ($\text{7b}$) was obtained in 91% yield.     

Structural features of diastereomeric oxazolidin-2-ones

Model diastereomeric oxazolidinones containing various substituents at positions 3 and 5 were synthesized. Several individual diastereomers bearing methyl groups at positions 4 and 5 in cis-and trans orientations were isolated. The TLC and ¹H NMR spectroscopic data suggest that diastereomers, particularly those containing the aryl substituent at position 5, are substantially different in the physical and spectral properties. The configurations of some diastereomers were established by X-ray diffraction and NOESY spectroscopy. For these compounds, the reliable assignment of the characteristic ¹H NMR signals of individual groups was made, which provided evidence for the cis or trans orientation of the methyl groups at positions 4 and 5. The scope of the method as applied to the determination of the cis and trans isomers from their ¹H NMR spectra is discussed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 133–139, January, 2007.     

Electrogenerated base-induced N-acylation of chiral oxazolidin-2-ones. Part 2

An improved and efficient electrochemical N-acylation of chiral oxazolidin-2-ones has been achieved. The generation of the nitrogen anion is obtained under mild conditions and without addition of base or probase, by direct electrolysis of a solution of MeCN-TEAP containing the oxazolidinone. Acylation agents (acid chlorides or anhydrides) were added at the end of the electrolysis. N-Acylated products were isolated in high to excellent yields.     

Synthesis of derivatives of oxazolidin-5-ones

A method has been developed for the synthesis of derivatives of oxazolidin-5-one by the reaction of the corresponding N-benzyloxycarbonylaminoacid with formaldehyde in the presence of formic acid. Yields of derivatives of 3-benzyloxycarbonyloxazolidin-5-one increase with increased molecular weight of the initial compound. For the synthesis of 3-benzyloxycarbonyl-4-benzyloxazolidin-5-one the proposed method gives a higher yield than previously known methods. The reaction mechanism is discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 115–117, January, 1993.     

Resolution of secondary arylalkyl alcohols using pentafluorophenyl 2-phenylbutanoate and zinc chloride

The resolution of racemic secondary arylalkyl alcohols using pentafluorophenyl 2-phenylbutanoate and zinc chloride is discussed. The levels of enantiomeric recognition were high leading to enantiomerically enriched alcohols in good yield.     

Enantioselective Michael additions on α,β-unsaturated N-acylated oxazolidin-2-ones using mild scandium triflate catalysis

The asymmetric conjugate addition of thiophenol to (E)-3-crotonoyloxazolidin-2-one catalysed by the scandium(III) triflate complex of Ph-PYBOX gave the corresponding adduct in 66% ee. Lanthanoid triflates gave lower enantioselectivities (?28% ee).     

Modified Mg : Al hydrotalcite in the synthesis of oxazolidin-2-ones

The modified Mg : Al (3 : 1) hydrotalcite has been found to be an efficient catalyst in the conversion of carbamates into oxazolidin-2-ones under mild reaction conditions. A wide variety of oxazolidin-2-ones were obtained with excellent chemical yield.     

Direct synthesis of oxazolidin-2-ones from tert-butyl allylcarbamate via halo-induced cyclisation

A novel synthetic pathway towards the 2-oxazolidinone derivatives involving the halo-induced cyclisation of tert-butyl allyl(phenyl)carbamate was successfully developed. Various halogenating reagents were evaluated under different reaction conditions for the reaction optimisation. Interestingly, the synthetic route to 2-oxazolidinone derivatives containing one halogen atom in the aliphatic site or two halogen atoms including the extra halogen atom substituted in the aryl group at the para position, were thoroughly established for all chloro-, bromo- and iodo compounds. Either halo-unsubstituted-aryl oxazolidinone or p-halo-substituted-aryl oxazolidinone could be selectively produced by selecting the appropriate choices of halogenated reagents and reaction conditions e.g. reaction time and temperature. Toloxatone, a commercial antidepressant, was successfully synthesized by using this developed method.     

Synthesis and structural study of new substituted chiral sulfamoyl oxazolidin-2-ones

The synthesis of new series of oxazolidinones having sulfonamide moieties is described. These compounds are synthesized in good yield starting prochiral 1,3-dichloro-2-propanol and chlorosulfonyl isocyanate. This strategy involves the formation of carboxylsulfamide by carbamoylation–sulfamoylation reaction followed by intermolecular cyclization. In order to determine the enantioselectivity during the cyclization step, X-ray studies of products are performed.     

New phenylselanyl group activation: synthesis of aziridines and oxazolidin-2-ones

After the study of different phenylselanyl group activators, halogenation by N-bromosuccinimide (NBS) has been shown to be the most suitable manner for cyclizing beta-phenylselanyl amines into aziridines and also enabled production of oxazolidin-2-ones from N-Boc beta-phenylselanyl amines in excellent yield.     

Development of new calcium receptors based on oxazolidin-2-ones containing pseudopeptides

With the aim of designing a new calcium receptor, the synthesis and the conformational analysis of a small library of dipeptides having the general formula Ac-Oxx-L-Xaa-OBn [Oxx = L-Oxd, (4S,5R)-4-methyl-5-carboxyoxazolidin-2-one; D-Oxd, (4R,5S)-4-methyl-5-carboxyoxazolidin-2-one; or D-Oxac (4R)-(2-oxo-1,3-oxazolidin-4-yl)-acetic acid] is reported. Ac-L-Oxd-L-Ala-OBn was identified as the most promising compound by MS-ESI analysis and this outcome was confirmed by photoluminescence spectroscopy.     

Resolution of (4RS,5RS)-4,5-diphenylimidazolidine-2-thione using pentafluorophenyl active esters

(4RS,5RS)-4,5-Diphenylimidazolidine-2-thione is resolved efficiently by treatment with NaHMDS and an enantiomerically pure pentafluorophenyl active ester. The levels of diastereocontrol were excellent (up to 90% de).     

An improved procedure for the palladium-catalyzed oxidative carbonylation of beta-amino alcohols to oxazolidin-2-ones

A highly efficient oxidative cyclocarbonylation of beta-amino alcohols and 2-aminophenol to oxazolidin-2-ones has been achieved by using PdI(2) in conjunction with KI as the catalytic system in DME under relatively mild conditions (100 degrees C and 20 atm of a 4:1 mixture of CO and air).     

Preparation of oxazolidin-2-ones by oxidation of oxazolidine-2-thiones. A proton magnetic resonance structural study

The preparation of a series of oxazolidine-2-thiones, both homochiral and racemic, as well as their oxidation to oxazolidin-2-ones is reported. X-Ray and pmr studies have showed that the stereochemical integrity of the starting aminoalcohol is maintained.     

Reaction of 2-{[2-(ethenyloxy)ethoxy]methyl}oxirane with oxazolidin-2-ones

Reactions of 2-{[2-(ethenyloxy)ethoxy]methyl}oxirane with N-unsubstituted oxazolidin-2-ones give mixtures of isomeric 3-{3-[2-(ethenyloxy)ethoxy]-2-hydroxypropyl}- and 5-{[2-(ethenyloxy)ethoxy]- methyl}-3-(2-hydroxyalkyl)oxazolidin-2-ones. If the initial oxazolidin-2-one contains two alkyl groups on C⁴, 3-{3-[2-(ethenyloxy)ethoxy]-2-hydroxypropyl}oxazolidin-2-ones are selectively formed.     

An easy one-pot stereoselective synthesis of 4-substituted and 4,5-disubstituted oxazolidin-2-ones from N-Boc-2,3-aziridino alcohols

A novel and efficient one-pot stereoselective transformation of N-(t-butoxycarbonyl)-2,3-aziridino alcohols into 4-substituted and 4,5-disubstituted oxazolidin-2-ones has been developed; these functionalized products are amenable to other elaborations, some of which are described.     

Experimental and theoretical investigations for the regio and stereoselective transformation of trans 1,2,3-trisubstituted aziridines into trans oxazolidin-2-ones

The regio and stereoselective transformation of trans 1,2,3-trisubstituted aziridines into trans oxazolidin-2-ones takes place in good yield. However, the cis configuration at C2 and C3 in monocyclic aziridines is a limiting factor for this transformation. Ab initio calculations show that while the ring-opening process assisted by iodide is regioselective, the subsequent ring-closure is responsible for the retention of the configuration at the trans oxazolidin-2-one. The larger energy found for the ring-closure process for the cis aziridines accounts for the non-formation of the cis oxazolidin-2-ones.